Time varying signals that are intended to occupy two logical states at various instances in time and therefore intended to reflect changes between two logical states, i.e. signals that are digital in nature, can be provided in a number of various environments where they are not reliable. This is especially the case in for instance systems for controlling electrical processes, such as for controlling generation and transmission of electrical power, i.e. high-voltage power transmission and generation systems, where a lot of system elements and devices for controlling such system elements may be provided in polluted or moist environments.
A digital contact transducer that is located in such a polluted or moist environment may for instance provide a rather low resistance, even when a contact of the transducer is open. If such a transducer is used for generating a digital signal, the transducer may in fact provide a signal that does not correctly reflect the logical state that is intended. In power transmission systems this may for example lead to the shutting down of power transmission. Such transducers should of course be designed to be resistant to moisture in the environment. However, also other aspects have to be considered, such as cost. The problem can therefore unfortunately not be 100% avoided.
In case the element in the system that causes the generation of the signal is floating or ungrounded or high impedance grounded, which may be the case with for instance a battery system in an electrical power transmission system, a ground fault may lead to a detection of a signal level that does not correctly represent the signal generated.
There is therefore a need for improvement in relation to these types of situations.
U.S. Pat. No. 6,816,816 describes a transducer fault detection system that transforms transducer measurements into slew rate measurements, and determines which, if any, of these measurements are anomalous. The change in slew rate is here furthermore detected through comparing sampled digitized voltage samples with a defined voltage window.
CA 1102879 describes comparing analog data in a slow channel and corresponding to the current in a power line of a power transmission system with data of a fast channel also corresponding to the current in the power line. There is no discussion about errors in logical states.
There is therefore a need for an improvement in the detection of the logical states intended to be provided by a signal.